Merge 'Add helper to convert io::clock::Instant to useable format ' from Preston Thorpe

I needed this for another PR

Reviewed-by: Pere Diaz Bou <pere-altea@homail.com>

Closes #2654

core/io/clock.rs

@@ -1,9 +1,31 @@
+use std::time::{Duration, SystemTime, UNIX_EPOCH};
+
 #[derive(Debug, Clone, Copy, PartialEq, Eq, PartialOrd, Ord)]
 pub struct Instant {
     pub secs: i64,
     pub micros: u32,
 }
 
+impl Instant {
+    pub fn to_system_time(self) -> SystemTime {
+        if self.secs >= 0 {
+            UNIX_EPOCH + Duration::new(self.secs as u64, self.micros * 1000)
+        } else {
+            let positive_secs = (-self.secs) as u64;
+
+            if self.micros > 0 {
+                // We have partial seconds that reduce the negative offset
+                // Need to borrow 1 second and subtract the remainder
+                let nanos_to_subtract = (1_000_000 - self.micros) * 1000;
+                UNIX_EPOCH - Duration::new(positive_secs - 1, nanos_to_subtract)
+            } else {
+                // Exactly N seconds before epoch
+                UNIX_EPOCH - Duration::new(positive_secs, 0)
+            }
+        }
+    }
+}
+
 impl<T: chrono::TimeZone> From<chrono::DateTime<T>> for Instant {
     fn from(value: chrono::DateTime<T>) -> Self {
         Instant {